Link checker

We occasionally get notices that some external link in the HTML
documentation doesn't work.  I figured it would be good to make a habit
out of running a link checker over the documentation, perhaps as part of
the release process.  The couple of command-line tools I tried for this
didn't really excite me, though, so I was wondering whether the web team
has a link checking routine in place, and whether that could be applied
to the documentation hosted on the web site.